A bandsaw utilizes a blade that is in the form of a continuous thin metal band that (the tool is named after this type of blade) is trained about two wheels of the bandsaw, one of which is driven so as to rotate the blade and the other of which is adjustable to control the angle of the blade. A bandsaw is the most flexible of wood cutting tools as it can be used to make straight and curved cuts, and also complex curved cuts since it uses a narrow blade which enables a workpiece to be rotated during the cutting action. The blade exerts a downward cutting force on the workpiece, which serves to hold the workpiece securely and provides a relatively safe cutting tool. Also, the narrow blade kerf requires less horsepower and creates much less waste in comparison to other wood cutting power tools.
A bandsaw employs a mechanism to prevent the backward movement of the blade during the cutting action which can result in the blade being moved or shoved off the wheels about which it is trained. On most bandsaws, a round wheel bearing called a "thrust bearing" is used for this purpose, and is located along the back of the blade, i.e. the edge of the blade opposite from the saw teeth. A thrust bearing is referred to by various names, such as "blade support", "roller guide", "bearings", "supports", and will be referred to as a thrust bearing in this description. Most bandsaws incorporate two thrust bearings, one located above and the other below the work table.
A bandsaw also includes a mechanism for preventing or reducing sideways movement or deflection of the blade during the cutting action, and also preventing excessive twisting of the blade when cutting curves. Bandsaws employ "guide blocks" for this purpose, which are sometimes also referred to as "blocks" or "pins", generally comprising two pairs of guide blocks with one pair positioned above the worktable and the other pair below the worktable and with the guide blocks of each pair located along opposite sides of the blade.
For the last 100 years, guide blocks have been made out of metal, either in the form of metal blocks or round metal rods, which was an appropriate choice of material for guide blocks when bandsaws were running at very slow speeds. However, the average wood cutting bandsaw now runs at very high speeds, such as in the range of about 2800 feet per minute. At this high speed, metal is no longer the appropriate material for use as guide blocks, principally due to the friction created between the guide blocks and the metal blade. The friction generates heat which shortens blade life, such as by causing premature blade failure and/or loss of tooth hardness. This is especially prevalent with narrow blades such as must be used for making tight curves, since narrow blades don't have sufficient mass to absorb and dissipate heat well. This can also result in burning of the wood workpiece. Another deleterious effect resulting from the friction created by metal guide blocks is that they cannot be set close to the blade to accurately hold the blade secure for very accurate work. Other problems arise from metal guide blocks as currently used on bandsaws. For example, metal guide blocks are very noisy during operation of the bandsaw. Further, metal guide blocks can accidentally touch the teeth of the blade, thereby destroying the set of the teeth and rendering the blade useless, if they are not set perfectly. Since metal guide blocks cannot adequately hold small or narrow blades in the bandsaw, they sometimes are replaced with roller bearings, which are very expensive. In view of these and other shortcomings of prior art guide blocks, we developed the present invention to provide new and improved guide blocks for bandsaw blades.
Our invention provides, in a bandsaw having a continuous blade trained about a pair of wheels, guide blocks for restricting sideways movement of the blade characterized in that the guide blocks are made from a fiber reinforced phenolic material impregnated with graphite. Our new guide blocks provide numerous advantages over the prior art metal guide blocks now used in bandsaws which will be fully discussed in the detailed description which follows.
As noted, one of the primary objectives of our invention was to provide improved guide blocks as replacements for metal guide blocks now currently used in bandsaws. Another principle objective was to provide new guide blocks for bandsaws which can dissipate heat more effectively than metal guide blocks and thereby eliminate the adverse effects of heat generated by friction as now experienced with prior art metal guide blocks. Yet another principle objective was to provide new guide blocks for bandsaw blades that will reduce friction between the guide blocks and the blade in comparison to prior art metal guide blocks and which also will not stain or discolor wood work pieces. Other more specific objectives will appear in the description which follows.